Schell Games, in partnership with WestEd, proposes to create a mobile adventure game entitled Only One Day in which middle-school players are able to experience the excitement of one day in an emergency department (ED) from the perspective of various ED roles (physicians, nurses, therapists, etc). Players will experience the same day multiple times across sessions, moving between physician and staff positions, completing associated medical tasks, and making decisions about patient care and physician and staff interactions and collaborations. To have a successful day and complete the game, players must use engineering design skills (as defined by the Next Generation Science Standards) to define problems (for both patients and staff), develop and test models of behavior, interpret evidence gained from these models, and use that evidence to inform their problem solving. Because players must experience the same day in multiple iterations, they must use information obtained during previous iterations of that day to inform how to effectively and efficiently solve problems with patients and staff. This game is designed to take place within 5, 20-min sessions. Each session will represent one day in the emergency room. By the final session, players should have developed enough knowledge about both their medical decisions for their patients and their between-character interactions to play the ideal day and, thus, beat the game. The project goals are to (1) develop and improve middle-school students' engineering design skills through gameplay, (2) familiarize students with ED professions, including required medical knowledge and steps to achieve this career goal, and (3) change the perception of racial and ethnic diversity within ED roles. WestEd will conduct usability and feasibility testing with students, teachers, and content experts to ensure that the Phase I product is the best possible one and provide useful information for development of future Phase II product plans.